Road Milling Machine For Working Road Or Ground Surfaces

ABSTRACT

A road milling machine includes a machine frame, front wheels or tracks, rear wheels or tracks, and a milling drum supported from the machine frame between the rear wheels or tracks. The front wheels or tracks are mounted on pivoting columns. Steering levers are attached to the pivoting columns. A steering tie rod includes a connecting part and a projecting arm. The connecting part is connected to the steering levers. A steering cylinder is connected to a free end of the projecting arm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a road milling machine for working road orground surfaces.

2. Description of the Prior Art

Such road milling machines are known, for example, from EP 0 836 659.

With such road construction machinery, in particular small millingmachines, good manoeuvrability of the road milling machine is of theessence. Such road milling machine must not only be suitable forstraight-ahead travel and normal cornering procedures, for example, butmust additionally be able to follow the course of narrow bends, forexample, when negotiating around traffic islands or a manhole cover.

In the known small milling machines, the milling drum therefore endsnearly flush with one outer side of the machine frame, the so-calledzero-clearance side. Due to this arrangement, it is possible to millvery close along obstacles. It has also already been known for thispurpose to pivot the rear wheel located on the zero-clearance sideinwards, relative to the zero-clearance side, from an outer end positionto an inner end position in front of the milling drum.

The possibility to follow the course of very narrow bends on saidzero-clearance side is of particular importance as it enables highlyprecise milling operations to be performed around very small obstacles.It has therefore already been known in such road milling machines todesign differently large steering angles for a cornering procedure tothe inside or to the outside respectively, relative to saidzero-clearance side, in particular to design an especially largesteering angle for a cornering procedure to the outside.

It is understood that, when the manoeuvrability is improved, the rangeof possible applications and the economic efficiency of such roadmilling machine can be improved.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to improve themanoeuvrability of a road milling machine, in particular of a smallmilling machine.

The above object is achieved, according to the invention, in that thewheel brackets of the wheels or crawler tracks of the front axle arecoupled to one another via a connecting part for synchronous adjustmentof the steering angles, and that said connecting part forms a steeringtie rod together with an arm projecting from the connecting part, wherethe arm of said steering tie rod is coupled to the free end of at leastone steering cylinder.

Such design of the connecting part enables an increase of the adjustablemaximum steering angle of the wheels or crawler tracks whilesimultaneously allowing a compact machine design.

For a steering movement in which the zero-clearance side of the roadmilling machine is on the inside, it is intended for the wheel bracketsto be coupled, via the connecting part, in such a fashion that, in thevertical plane of the rear axle or the extension of the same in the areaof the rear wheel or crawler track, the center of rotation of both frontwheels or crawler tracks is arranged as close as possible to thezero-clearance side.

As the milling drum axis lies in the same vertical plane as the rearaxle of the rear wheels or crawler tracks, this arrangement enables themilling, with the front end of the milling drum on the zero-clearanceside, of narrow bend radii, for example, around manhole covers.

The increase of the maximum possible steering angle enables the distanceof the current center of rotation to the front end of the milling drumlocated on the inner side of the bend to be shortened, thereby allowingnarrower bend radii to be driven.

In this design, it is intended for the arm of the steering tie rod toextend between the pivoting columns of the wheels or crawler tracks awayfrom the connecting part, with the connecting part and the steeringcylinder being arranged on opposite sides, as seen in the direction oftravel, relative to an imagined connecting line of the pivoting axes.

It is preferably intended for the wheels or crawler tracks to besteerable between two steering angle end positions for a direction oftravel to the left or to the right, where the connecting part exhibitscurved sections or cut-outs in such a fashion that, in the endpositions, the connecting part maintains a distance from the respectivepivoting axis that is larger than the radius of the respective pivotingcolumn.

In a preferred embodiment, the arm of the steering tie rod projectsessentially centrally from the connecting part. The initially centralarrangement of the arm offers the advantage that collision freedomrelative to the pivoting columns is enabled for a larger area. In frontof the area of the pivoting columns as seen in the direction of travel,the arm may be of curved or angled design.

It is preferably intended for the arm of the steering tie rod projectingfrom the connecting part to extend behind the pivoting columns in anapproximately parallel fashion to the steering cylinder and, at the freeend, to be connected in an articulated fashion to a single steeringcylinder. In this way, the respective points of force application arelocated on opposite sides relative to the pivoting columns.

It is preferably intended for the arm projecting from the connectingpart to feature a width that ranges between the 0.5-fold and 0.97-fold,preferably between the 0.75-fold and 0.95-fold of the difference betweenthe distance of the pivoting axes and the twofold radius of the pivotingcolumns.

The steering levers may be arranged at the pivoting columns in differentangular positions relative to the direction of travel in such a fashionthat different maximum steering angles result for a steering directionto the right or left.

The pivoting columns of the front axle may be mounted in a cross member.

The fixed point of the steering cylinder is preferably arranged at themachine frame or at the cross member.

In a preferred embodiment, the cross member may be pivotable, relativeto the machine frame, about a swing axle extending in the direction oftravel. In this manner, it is also possible for the wheels or crawlertracks of the front axle to run on different planes.

It is preferably intended for the rear wheel located on thezero-clearance side to be pivotable inwards, relative to thezero-clearance side, from an outer end position in which the wheel isbeyond the zero-clearance side and the rear axles of both rear wheelsare in alignment, to an inner end position in front of the milling drum.

It may be intended, as a minimum, for the rear wheel on thezero-clearance side to be steerable.

The steerability, possibly of both rear wheels but as a minimum of therear wheel located on the zero-clearance side, likewise improves themanoeuvrability of the road milling machine. It is particularlyadvantageous when crawler tracks are used.

A particularly preferred embodiment intends for the wheels or crawlertracks of the front axle as seen in the direction of travel to bearranged offset to one another in such a fashion that the wheel on theinside relative to the steering direction, or the wheel or crawler trackon the zero-clearance side is arranged in front of the neighbouringwheel or crawler track as seen in the direction of travel.

The offset arrangement of the wheels or crawler tracks offers theadvantage that, on account of the offset, the steering geometry permitslarger maximum steering angles to be adjusted, which allows a narrowbend radius to be driven. This improvement is of major advantage inparticular when performing a cornering procedure in which thezero-clearance side is located on the inside.

Ultimately, the offset arrangement of the front wheels allows the bendradii of both front wheels to be matched to one another while at thesame time reducing the distance of the current center of rotation fromthe front end of the milling drum. Matching the bend radii of both frontwheels enables a more precise cornering procedure, and shortening thedistance of the center of rotation to, for example, the front end of themilling drum on the zero-clearance side allows extremely narrow bendradii of up to 130 mm and less to be achieved. As a result, the roadmilling machine can practically turn on the spot.

The invention also enables a better manoeuvrability of the road millingmachine than before to be achieved in the event of a requiredlengthening of the wheelbase.

Lengthening of the wheelbase may become necessary, among other things,due to the use of a new and more complex engine technology or theintegration of additional components, for example, for theafter-treatment of exhaust gases. These components require additionalconstruction space but are necessary in order to comply with emissiondirectives.

It is preferably intended for the offset between the pivoting axes ofthe front axle as seen in the direction of travel to be between 50 mmand 350 mm, preferably between 100 mm and 250 mm. Such offset in thearrangement of the pivoting axes of the wheels or crawler tracks of thefront axle allows a significant increase of the maximum steering angles.

It is preferably intended for the steering angle to the outside of thewheel or crawler track located on the zero-clearance side to beadjustable up to a maximum steering angle in excess of 70°, preferablybetween 70° and 90°.

A preferred embodiment intends for the offset of the wheels or crawlertracks of the front axle to be chosen in such a fashion that the wheelsor crawler tracks in the steering direction to the outside relative tothe zero-clearance side both run in a single track.

This offers the advantage that the road milling machine can be turned onthe spot, that is, essentially around the current center of rotation,thus allowing the milling of extremely narrow bend radii. Furthermore,this arrangement allows a more precise cornering procedure.

In a further embodiment, it may be intended for the cross member to bepivotable about a vertical axis. This feature enables the offset of thefront wheels to be optionally provided either on the zero-clearance sideor on the side opposite the zero-clearance side so that, in each case,the wheel located on the inside relative to the steering direction canbe arranged in front of the neighbouring wheel. In this way, it can beachieved that the bend radii of the front wheels are matched to oneanother even when steering to the left relative to the zero-clearanceside, which enables the distance between the front end of the millingdrum facing away from the zero-clearance side and the center of rotationin the form of an axis of rotation extending essentially orthogonally tothe ground surface to be likewise reduced further.

It is preferably intended for the wheel brackets to be coupled via theconnecting part in such a fashion that, when steering to the outsiderelative to the zero-clearance side, the center of rotation exhibits adistance from the outer front end of the milling drum of less than 250mm, preferably less than 150 mm.

For a cornering procedure in which the zero-clearance side is on theoutside, it is intended for the wheel brackets to be coupled via theconnecting part in such a fashion that, when steering to the insiderelative to the zero-clearance side, the center of rotation of bothfront wheels or crawler tracks exhibits, on the extension of the rearaxle, a distance from the inner front end of the milling drum that issmaller than the wheelbase, preferably smaller than 2,000 mm.

In the following, embodiments of the invention are explained in moredetail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is shown:

FIG. 1 a generic road milling machine in accordance with prior art,

FIG. 2 a top view of the road milling machine shown in FIG. 1,

FIG. 3 a top view of an embodiment of a steering tie rod,

FIG. 4 a side view of the front axle,

FIG. 5 a schematic illustration of the steering angles in a road millingmachine according to FIG. 1,

FIG. 6 a schematic illustration of the adjustable steering angles in afirst embodiment of the invention, and

FIG. 7 a schematic illustration of the adjustable steering angles in afurther embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a road milling machine for milling off roadways with aself-propelled chassis comprising a steerable front axle 6 with twofront wheels 10, 12 and two mutually independent rear wheels 14, 16. Itis understood that the wheels 10 to 16 may be substituted, wholly or inpart, by crawler tracks.

The chassis supports a machine frame 8, on which an operator's platform4 is located on the so-called zero-clearance side 24 of the roadconstruction machine in accordance with FIG. 2. The rear wheels 14, 16are height-adjustable by means of lifting columns 48 in order to be ableto use them to adjust the working depth of a milling drum 20.

With its front end on the zero-clearance side, the milling drum 20 isnearly flush with the zero-clearance side 24 of the machine frame sothat working close to the edge is possible on the zero-clearance side 24of the road milling machine. To this effect, the wheel 16 is pivotedinwards, from an outer end position 26 beyond the plane of thezero-clearance side, in front of the milling drum and into a cut-out 18of the machine frame 8 so that the outer edge of the wheel 16 can endflush with the zero-clearance side 24 or even assume an end positionfurther inside relative to the zero-clearance side 24. The rear wheel 16or both rear wheels 14, 16 may be steerable.

As can best be inferred from FIG. 1, the milling drum axis 22 extendsessentially in the same vertical plane as the axles 7 of the wheel 14and of the wheel 16 in the outer end position 26.

The circle of engagement of the milling drum 20 ends close to the rearend of the machine frame 8 so that milling close to the edge is possibleright up into corners.

FIG. 3 shows a steering tie rod 30 with a connecting part 40 whichconnects the steering levers 36 of both front wheels 10, 12 in anarticulated fashion. An arm 50 projects initially essentially centrallyfrom and preferably orthogonally to said connecting part 40.

The wheel brackets 32 are each connected with pivoting columns 34, saidpivoting columns 34 being mounted in a cross member 56 to pivot aboutone each pivoting axis 38.

The steering levers 36 are connected with the wheel brackets 32 in apermanent fashion.

The arm 50 projecting essentially orthogonally from the connecting part40 exhibits, on the sides facing the pivoting columns 34, a curvedcontour 52, 54 that is adapted to the diameter of the pivoting columns34 in order to be able to adjust maximum steering angles without causingany collision.

Above an imagined connecting line between the pivoting axes 38 of thepivoting columns 34, the arm 50 may be angled or curved in order to beconnected, at its free end, to a steering cylinder 44 which transfersthe force required for steering to the steering tie rod 30. The steeringcylinder 44 is in turn directly or indirectly articulated at a fixedpoint 42 relative to the machine frame 4.

FIG. 4 shows a side view of the front axle with wheels 10, 12 offset toone another, the pivoting columns 34 of said wheels 10, 12 being mountedin a cross member 56.

The cross member 56 is articulated at a plate 58 attached to the machineframe 8 in such a fashion that the cross member 56 may be pivotable,relative to the machine frame 8, about a swing axle extending in thedirection of travel.

In an alternative embodiment, it may also be intended for the crossmember 56 to be pivotable about a vertical axis extending parallel tothe pivoting axes 38 in such a fashion that the offset “d” canoptionally be provided on the left or right as seen in the direction oftravel so that, in each case, the wheel 10 or 12 located on the insiderelative to the steering direction can be arranged in front of theneighbouring wheel as seen in the direction of travel.

FIG. 5 shows an embodiment according to prior art together with thegeometrical distances relevant for the milling operation. The left-handillustration of FIG. 5 indicates the wheelbase “a” of the road millingmachine. The middle illustration shows, as a characteristic relevant forthe milling operation, the distance “b” of the center of rotation “D”from the front end of the milling drum 20 facing away from thezero-clearance side when adjusted to the maximum steering angle to theleft.

The right-hand illustration of FIG. 5 shows the same situation whenadjusted to the maximum steering angle to the right in which thezero-clearance side 24 is located on the inner side of the bend. Notonly the adjustable maximum steering angle of the front wheels 10, 12 isof great importance in this arrangement but also the distance “c” of thecenter of rotation D to the front end of the milling drum 20 on thezero-clearance side 24. It is understood that a smaller distance “c”allows the milling of narrower bend radii. Moreover, a shortening of thedistance “b”, or a possibly required extension of the wheelbase “a” andsimultaneous reduction of the distances “b” and “c”, is also desirable.

FIG. 6 shows an embodiment of the invention in which the front wheels10, 12 are arranged offset to one another. The wheelbase “a” of thefront right wheel 12 has been maintained while the front left wheel 10is moved back by an offset “d”. Said offset “d” may, for example, be ina range between 50 mm to 350 mm, preferably between 100 mm and 250 mm.

Firstly, said offset offers the advantage inferable from the middleillustration of FIG. 6 that the steering angle of the front right wheel12 can be increased, which allows the distance “b” between the center ofrotation and the left front end of the milling drum 20 to be shortenedsignificantly, thus also improving the manoeuvrability of the roadmilling machine to the inside relative to the zero-clearance side 24.

It can be inferred from the right-hand illustration of FIG. 6 that themaximum steering angle can be increased to, for example, 75° as a resultof the offset arrangement of the front wheels 10, 12, thus enabling thedistance “c” of the center of rotation “D” to the front end of themilling drum 20 on the zero-clearance side 24 to be reducedsignificantly, that is, by approx. 20% in comparison with FIG. 5.

FIG. 7 shows the employment of a steering tie rod 30 in addition to theoffset “d” of the front wheels 10, 12, where said steering tie rod 30allows a larger steering angle at least with regard to the left wheel10, as can be inferred from the middle illustration of FIG. 7, so thatthe distance “b” can be reduced further in comparison with FIG. 4.

When steering to the right, the steering angles of both front wheels 10,12 can be increased further so that the distance “c” can be reduced byapprox. 65% in comparison with FIG. 5, thus allowing extremely smallbend radii to be milled when steering to the right relative to thezero-clearance side. The distance “c” achieves a dimension of less than150 mm. A value of, for example, approx. 1700 mm is achievable for “b”.

The embodiments according to FIGS. 6 and 7 offer a further advantage inthat, when adjusted to the maximum steering angle to the outside as seenfrom the zero-clearance side, the front wheels 10, 12 can be driven in amore or less similar radius so that the wheels 10, 12 essentially run inthe same track.

This arrangement offers the advantage of a more precise corneringprocedure.

Maximum steering angles in excess of 70°, preferably between 70° and90°, can be adjusted.

The embodiment in FIG. 6 shows steering angles of the front wheels 10,12 of between 55° and 75°, while steering angles of the front wheels ofbetween 59° and 79° can be inferred from the embodiment in FIG. 7.

What is claimed is:
 1. A road milling machine for working road or groundsurfaces, comprising: a machine frame including a lateral outer side;left and right front wheels or crawler tracks, and left and right rearwheels or crawler tracks, supporting the machine frame; a milling drumsupported from the machine frame between the rear wheels or crawlertracks, the milling drum including an end located substantially flushwith the lateral outer side of the machine frame such that the lateralouter side defines a zero-clearance side to enable milling close toobstacles; left and right height adjustable lifting columns connectingthe left and right rear wheels or tracks to the machine frame such thata milling depth of the milling drum is adjustable by adjusting a heightof the lifting columns; left and right pivoting columns connecting theleft and right front wheels or tracks to the machine frame, eachpivoting column having a pivot axis; left and right steering leversconnected to the left and right front wheels or tracks, respectively, soas to steer each of the front wheels or tracks in steering angles aboutthe pivot axes of their respective pivot columns; a steering tie rodincluding a rigid connecting part and an arm projecting from theconnecting part, the connecting part coupling the steering levers of thefront wheels or tracks to one another for synchronous adjustment of thesteering angles; and at least one steering cylinder including a free endcoupled to the arm of the steering tie rod to adjust the steeringangles.
 2. The machine of claim 1, wherein: the arm of the steering tierod extends away from the connecting part and between the pivotingcolumns, with the connecting part and the steering cylinder beingarranged on opposite sides of an imaginary line connecting the pivotaxes of the pivoting columns.
 3. The machine of claim 2, wherein: thefront wheels or tracks are steerable between two end positions for adirection of travel to the right or left, and the arm of the steeringtie rod has first and second curved sections configured such that in theend positions the connecting part maintains a distance from therespective pivot axis that is larger than a radius of the respectivepivoting column.
 4. The machine of claim 3, wherein: the pivotingcolumns each have a radius; and the first and second curved sections ofthe arm of the steering tie rod are located on both sides of the armwhere the arm projects from the connecting part, which curved sectionsface the pivoting columns and are complementary to the radii of thepivoting columns.
 5. The machine of claim 1, wherein: the arm of thesteering tie rod projects substantially centrally from the connectingpart.
 6. The machine of claim 1, wherein: the at least one steeringcylinder is a single steering cylinder; and the arm of the steering tierod extends behind the pivoting columns approximately parallel to thesteering cylinder, and the arm includes a free end connected in anarticulated fashion to the steering cylinder.
 7. The machine of claim 1,wherein: the pivoting columns each have a radius; and the arm projectingfrom the connecting part has a width in a range of from 50% to 97% of adifference between a distance between the pivot axes and the combinedradii of the two pivoting columns.
 8. The machine of claim 1, wherein:the pivoting columns each have a radius; and the arm projecting from theconnecting part has a width in a range of from 75% to 95% of adifference between a distance between the pivot axes and the combinedradii of the two pivoting columns.
 9. The machine of claim 1, wherein:the left and right steering levers are oriented relative to the pivotaxes of the left and right pivoting columns in different angularpositions relative to the direction of travel, such that the left andright front wheels or tracks have different maximum steering angles fromeach other when steered either to the right or to the left.
 10. Themachine of claim 1, wherein: the left and right pivoting columns aremounted in a cross member.
 11. The machine of claim 10, wherein: the atleast one steering cylinder is articulated at a fixed point located onthe cross member.
 12. The machine of claim 10, wherein: the cross memberis pivotable, relative to the machine frame, about a swing axleextending in the direction of travel.
 13. The machine of claim 1,wherein: the at least one steering cylinder is articulated at a fixedpoint located on the machine frame.
 14. The machine of claim 1, wherein:one of the left or right wheels or tracks is offset in front relative tothe other in the direction of travel.
 15. The machine of claim 14,wherein: the one wheel or track offset to the front is on the insiderelative to a steering direction.
 16. The machine of claim 15, wherein:the cross member is pivotable about a vertical axis such that the frontwheel or track located on the inside relative to the steering directioncan be offset in front relative to the other front wheel or track. 17.The machine of claim 14, wherein: the one wheel or track offset to thefront is on the zero-clearance side.
 18. The machine of claim 14,wherein the pivot axes of the left and right pivoting columns are offsetin the direction of travel by an offset distance in a range of from 50mm to 350 mm.
 19. The machine of claim 18, wherein the offset distanceis in a range of from 100 mm to 250 mm.
 20. The machine of claim 1,wherein: at least one of the rear wheels or tracks is steerable.
 21. Themachine of claim 1, wherein: the rear wheel or track located on thezero-clearance side is pivotable inwards, relative to the zero-clearanceside, from an outer end position in which the wheel or track is beyondthe zero-clearance side and the rear wheels or tracks are aligned, to aninner end position in front of the milling drum.